Such cutting inserts are used for example in the external milling of crankshafts, in particular for the machining of the undercut on the crank pin. In EP 0 830 228 [U.S. Pat. No. 6,374,472], an external milling disk is described that is driven in such a way that machining is done at cutting speeds of over 160 m/min. In doing so, both the crankshaft and the external milling disk are rotated. Tangentially clamped cutting inserts are used for the machining of the cylindrical surfaces of the rotated workpiece, for example the crankpin surface, while radially clamped cutting inserts are used for the machining of the cheeks, an oil flange and an undercut. Such cutting inserts have the structure described above, each with rounded cutting edges that have an at least essentially uniform curvature about an angle of approximately 135° and that merge here immediately to a straight segment, before the cutting edge merges via a convex curvature into the opposite end face.
For the machining of crankshafts, turning tools are known in the prior art that are used in the so-called turn-broach or turn-turn-broach method. In turn broaching, a straight turn broach tool is advanced radially onto the rotating workpiece to be machined. In turn-turn broaching, multiple cutting inserts in series are positioned around a reference circumference of a disk-shaped tool carrier and are gradually steadily indexed along an initial section of the disk circumference. This tool is pivoted inward along a reference arc in the radial direction onto the rotated tool, as described in principle in EP 0 313 644 [U.S. Pat. No. 4,790,698] or EP 0 286 771. On these bar- or disk-shaped tools as well, two geometrically different types of cutting inserts are used for the pin machining and the formation of the undercut.
Beside the methods described above, so-called internal milling is also known in the prior art, in which the work is likewise done using a disk-shaped milling tool, but with the proviso that the cutting inserts are positioned on the inner periphery of an annular disk.
The tool costs are comprised of multiple components. These include in particular those tool costs that are determined not only by the pure manufacturing costs, but also by the tool life. In addition, machining times and the costs of tool replacement are also included. So-called indexable inserts have multiple usable cutting blades, although the number of them is limited by the design. For instance, the number of usable cutting edges in a cutting insert mentioned at the start is limited to four.